Method for making thermionic electron emission device

Abstract

A method for making a thermionic electron emission device. The method includes the following steps. First, an insulating substrate is provided. Second, a number of lattices are formed on the insulating substrate. Third, a first electrode and a second electrode are fabricated in each lattice on the insulating substrate. Fourth, a carbon nanotube film structure is provided and at least part of the carbon nanotube film is suspended structure above the insulating substrate. Sixth, excess carbon nanotube film structure is cut away to obtain a number of thermionic electron emitters. The thermionic electron emitters are spaced from each other and located between the first electrode and the second electrode in each lattice.

What is claimed is: 
     
       1. A method for making a thermionic electron emission device, the method comprising:
 (a) providing an insulating substrate; 
 (b) forming a plurality of lattices on the insulating substrate; 
 (c) fabricating a first electrode and a second electrode in each lattice on the insulating substrate; and 
 (d) providing a carbon nanotube film structure and suspending at least part of the carbon nanotube film structure above the insulating substrate; and 
 (e) cutting away excess carbon nanotube film structure to obtain a plurality of thermionic electron emitters spaced from each other and located between the first electrode and the second electrode in each lattice. 
 
     
     
       2. The method of  claim 1 , wherein step (d) is executed by placing the carbon nanotube film structure on surfaces of the first electrodes and the second electrodes far from the substrate so that part of the carbon nanotube film structure is suspended by the first electrode and the second electrode. 
     
     
       3. The method of  claim 1 , further comprising a step of forming a plurality of recesses on a surface of the insulating substrate corresponding to the plurality of lattices respectively before step (d). 
     
     
       4. The method of  claim 3 , wherein the step of forming the recesses is executed by etching the substrate. 
     
     
       5. The method of  claim 3 , wherein the recesses are uniformly-spaced and have a predetermined size. 
     
     
       6. The method of  claim 3 , wherein the carbon nanotube film structure is placed on the substrate to cover the recesses on the substrate, and the first electrode and the second electrode are formed on a surface of the carbon nanotube film structure to fix the carbon nanotube film structure. 
     
     
       7. The method of  claim 6 , wherein part of the carbon nanotube film structure is suspended by the recesses. 
     
     
       8. The method of  claim 1 , wherein step (b) is executed by a method selected from the group consisting of a screen-printing method, an evaporation method, and a sputtering method. 
     
     
       9. The method of  claim 8 , wherein step (b) is executed by the screen printing method, and the screen printing method for making the lattices comprises:
 screen printing a plurality of uniformly-spaced first electrode down-leads and second electrode down-leads parallel to each other on the insulating substrate; 
 screen printing a plurality of uniformly-spaced insulating layers on the first electrode down-leads and second electrode down-leads; and 
 screen printing a plurality of third electrode down-leads and fourth electrode down-leads on the insulating layers parallel to each other on the insulating substrate. 
 
     
     
       10. The method of  claim 9 , wherein step (c) is executed by fabricating the first electrode in each lattice and in contact with the first electrode down-lead and the second electrode in each lattice and in contact with the third electrode down-lead via a screen-printing method, an evaporation method, or a sputtering method. 
     
     
       11. The method of  claim 10 , wherein the first electrode and the second electrode in each lattice are spaced from each other. 
     
     
       12. The method of  claim 1 , wherein step (d) comprises:
 (d1) providing at least one carbon nanotube film; and 
 (d2) applying the at least one carbon nanotube film on the electrodes. 
 
     
     
       13. The method of  claim 12 , wherein step (d2) is executed by applying a single carbon nanotube film on the electrodes along a direction extending from the first electrode to the second electrode; or applying at least two stacked carbon nanotube films on the insulating substrate such that carbon nanotubes of one carbon nanotube film are oriented at an angle with respect to carbon nanotubes of the adjacent carbon nanotube film. 
     
     
       14. The method of  claim 12 , wherein step (d2) comprises:
 (d21) supplying a supporting element; 
 (d22) applying at least two carbon nanotube films on the supporting element; 
 (d23) cutting away any excess portion of the at least two carbon nanotube films; 
 (d24) treating the at least two carbon nanotube films structure with an organic solvent; 
 (d25) removing the at least two carbon nanotube films from the supporting element to form a free-standing carbon nanotube film structure; and 
 (d26) applying the free-standing carbon nanotube film structure on the insulating substrate. 
 
     
     
       15. The method of  claim 14 , wherein in the step d22, the at least two carbon nanotube films are stacked with each other such that carbon nanotubes of one carbon nanotube film are oriented at an angle with respect to carbon nanotubes of the adjacent carbon nanotube film, the angle being in a range from about 0° to about 90°. 
     
     
       16. The method of  claim 1 , wherein step (e) is executed by a laser ablation method, or an electron beam scanning method. 
     
     
       17. The method of  claim 9 , wherein step (e) is executed by the laser ablation method, the laser ablation method comprising:
 (e1) scanning the carbon nanotube film structure along each first electrode down-lead via a laser beam; and 
 (e2) scanning the carbon nanotube film structure along each third electrode down-lead via a laser beam to cut the carbon nanotube film structure applied on the insulating substrate except that between the first electrodes and the second electrodes. 
 
     
     
       18. The method of claimed in  claim 17 , wherein in step (e1), a width of the laser beam is equal to a distance between the adjacent first electrodes along an aligned direction of the third electrode down-lead. 
     
     
       19. The method of claimed in  claim 17 , wherein in step (e2), a width of the laser beam is equal to a distance between adjacent first electrodes and second electrodes in adjacent lattices respectively along an aligned direction of the first electrode down-lead. 
     
     
       20. The method of claimed in  claim 1 , further comprising a step of forming at least one fixing electrode on the carbon nanotube film structure corresponding to the first electrode and the second electrode.